1. Field of the Invention
This invention relates to an automatic temperature control for a clothes washing machine.
2. Description of the Prior Art
Various methods and devices have been proposed in the past for controlling the temperature of the liquid added to a clothes washing machine to arrive at a final desired temperature of the wash fluid.
U.S. Pat. No. 3,707,857 discloses an automatic washer that utilizes a temperature sensor for controlling the water inlet valves to produce the desired temperature in the wash bath.
U.S. Pat. No. 4,330,081 provides a water temperature control system for a clothes washing machine in which the temperature of the incoming mixed hot and cold water is periodically sensed, and the accumulated average temperature of the mixed water is compared to a desired temperature value stored in the memory of a microprocessor. When the comparison results in a temperature difference which exceeds a predetermined error limit, the appropriate hot and/or cold water valves are turned off or on causing the average temperature of the mixed water to change toward the desired temperature value.
U.S. Pat. No. 4,147,297 discloses a temperature sensing system for controlling the temperature of fill water in an automatic washer in which the user may select one of two temperature levels and the control system will fill the washer with water at a temperature at or below the selected temperature. The inlet hot water valve is continuously held open during the fill process and the cold water valve is opened only when the hot water temperature is above the selected temperature level.
The prior art devices and methods have a drawback in that they do not provide a precise final temperature of the wash bath with a minimum number of cycles of the inlet control valves. The wash bath provided is either of a temperature not necessarily that selected by the user, or else there is excessive cycling of the inlet valves with the attendant wear thereof.